Next story in Science

If you've ever wondered where — and why — earthquakes happen the
most, look no further than a new map, which plots more than a
century's worth of nearly every recorded earthquake strong enough
to at least rattle the bookshelves.

The map shows earthquakes of magnitude 4.0 or greater since 1898;
each is marked in a lightning-bug hue that glows brighter
with increasing magnitude.

The overall effect is both beautiful and arresting, revealing the
silhouettes of Earth's tectonic boundaries in stark, luminous
swarms of color.

The map's maker, John Nelson, the user experience and mapping
manager for IDV Solutions, a data visualization company, said the
project offered several surprises.

"First, I was surprised by the sheer amount of earthquakes that
have been recorded," Nelson told OurAmazingPlanet. "It's almost
like you could walk from Seattle to Wellington [New Zealand] if
these things were floating in the ocean, and I wouldn't have
expected that."

In all, 203,186 earthquakes are marked on the map, which is
current through 2003. And it reveals the
story of plate tectonics itself.

The long volcanic seams where Earth's crust is born appear as
faint, snaking lines cutting through the world's oceans. The
earthquakes along these so-called spreading centers tend to be
rather mild. The best studied spreading center, called
the Mid-Atlantic Ridge, bisects the Atlantic Ocean, on the
right side of the image.

Its Pacific counterpart wanders along the eastern edge of the
Pacific Ocean, cutting a wide swath offshore of South America.
Another spreading center makes a jog though the Indian Ocean and
up through the Red Sea.

Subduction zones, the places where tectonic plates overlap and
one is forced to dive deep beneath the other and into the Earth's
crushing interior — a process that generates the
biggest earthquakes on the planet — stand out like a Vegas
light show.

Nelson said this concept hit home particularly for the Ring of
Fire, the vast line of subduction zones around the northern and
western edge of the Pacific Ocean.

"I have a general sense of where it is, and a notion of plate
tectonics, but when I first pulled the data in and started
painting it in geographically, it was magnificent," Nelson said.
"I was awestruck at how rigid those bands of earthquake activity
really are."

That realization prompted one big decision about the map's
design, Nelson said. Unlike many maps made in the United States,
this one is centered over the Pacific Ocean. "That looked like
where the magic was happening," Nelson said. California, a spot
rattled by quakes where faults jolt horizontally, also shines
brightly.

Teaching tool

There are undoubtedly many earthquakes missing, given the
dramatic change in scope and accuracy of seismological
instruments from 1898 to the present day. Nelson said he saw a
huge jump in the volume of data from the 1960s forward. Yet even
without the complete catalog of earthquakes, the map provides a
striking visual reference — even though none of the data are new.

All the earthquake information and maps are freely available on
the Internet courtesy of the U.S. Geological Survey, university
and state partners in California, and NASA.

"There's nothing new about plotting earthquakes," Nelson said.
"It's just presenting it in an interesting way."

And although he was modest about his own role as a designer,
Nelson emphasized the value of design in making data more
engaging. The project was a follow-up to a recent map
of more than 50 years of tornado tracks across the
United States; he said both maps are designed to get people more
interested in the larger phenomena behind them. "To get them to
start asking questions," Nelson said.